1. Field of the Invention
The present invention relates to a semiconductor package, and more particularly to a semiconductor package which can avoid solder bridge.
2. Description of the Related Art
FIGS. 1 to 4 show schematic views of a method for making a conventional semiconductor package. As shown in FIG. 1, a substrate 11 is provided. The substrate 11 has a first surface 111, a second surface 112, a plurality of first pads 113, a plurality of second pads 114, a Ni/Au plating layer 115 and a solder mask 116. The first pads 113 are exposed to the first surface 111. The second pads 114 are exposed to the second surface 112. The Ni/Au plating layer 115 is formed on the entire upper surface of the first pad 113. The solder mask 116 contacts the Ni/Au plating layer 115 directly, and has at least one opening so as to expose part of the Ni/Au plating layers 115. Then, a chip 12 is mounted on the substrate 11, and a plurality of conductive elements (for example, a plurality of wires 13) are formed so as to electrically connect the chip 12 and the first surface 111 of the substrate 11. Then, a plurality of first conductors (for example, a plurality of first solder balls 14) are formed on the Ni/Au plating layer 115.
As shown in FIG. 2, a molding compound 15 is formed on the first surface 111 of the substrate 11, so as to encapsulate the chip 12, the wires 13 and the first solder balls 14. As shown in FIG. 3, a plurality of second solder balls 16 are formed on the second pads 114, and the second solder balls 16 are reflowed. As shown in FIG. 4, part of a periphery area of the molding compound 15 is removed, so that the molding compound 15 has at least two heights, and one end of the first solder balls 14 is exposed. Thus, the conventional semiconductor package 1 is formed.
The conventional semiconductor package 1 has the following disadvantages. First, the solder mask 116 contacts the Ni/Au plating layer 115 directly, however the solder mask 116 and the Ni/Au plating layer 115 has low bonding strength, therefore delamination between the solder mask 116 and the Ni/Au plating layer 115 occurs easily. Moreover, the Ni/Au plating layer 115 disposed on the first solder balls 14 is encapsulated by the molding compound 15, and when the second solder balls 16 are reflowed, the first solder balls 14 expand because of high temperature. Meanwhile, the first solder balls 14 extrude to adjacent elements and protrude to the interface between the solder mask 116 and the Ni/Au plating layer 115 which has low bonding strength. As a result, it leads to the bridge between the first solder balls 14, as shown in area A of FIGS. 3 to 5, and the yield rate of the semiconductor package is decreased.
Therefore, it is necessary to provide a semiconductor package to solve the above problems.